A. Field of the Invention
The present invention relates to dryers and methods of drying, and in particular, dryers and methods of drying relatively small lots of product.
B. Problems in the Art
There are a number of situations that utilize forced air drying techniques. Many are large-scale drying systems concerned with processing large volumes of product per unit of time. There are other situations that require air drying of what would be called small lots of product. Drying smaller lots would not require the scale of equipment necessary for large lots. In fact, the use of large lot equipment for drying small lots would many times be inefficient.
An example of small lot drying is the drying of ear corn for seed conditioning purposes. Ear corn in lots of up to about 50 bushels is harvested and dried for maximum quality of seed for replanting.
The term "small lot" with regard to seed corn is defined herein as up to several tens of bushels, for example, up to around 50 bushels. It is difficult to justify utilizing dryers for large lots (e.g. well over 50 bushels) to dry small lots because of their cost, complexity, size, and operation. Seed corn must be dried right or its value might be lost. It can be extremely valuable (on the order of thousands of dollars per bushel). It is usually harvested as soon as possible to avoid degradation by insects, disease or weather. However, such early harvesting generally means that the moisture content of the corn is relatively high (e.g. 40%).
To maintain the quality of the seed, it is desirable to dry to seed corn immediately after harvesting. If it were not dried, it would be especially susceptible to degradation by, for example, molds or fungi. However, the drying process must occur correctly or the seed corn may be damaged.
Generally, it is preferred to dry by taking away a certain percent of moisture over each time period. For example, one guide is to take away 1% moisture every 4 hours. Thus, a bin of seed corn at 40% harvested moisture could take 112 hours, or almost 5 days to dry. Therefore, there is a need in the art to dry the corn at as close to the ideal rate as possible. If heated air is used that is too hot, it could damage or even kill the seed. If drying is too slow, the seed become susceptible to mold or fungi. Furthermore, slow drying is not optimal use of time and resources.
A further complication is that each collection of seed to be dried will not have identical drying needs. Therefore, there is a need in the art for the ability to adjust drying to individual needs of each lot being dried. Conventional small lot dryers provide a source of heated air flow. However, the temperature of the air is not adjustable on a bin to bin basis, but is constant for all bins sharing a plenum.
U.S. Pat. No. 5,893,218 describes a dryer that holds larger lots (e.g. from about 50 to 1,000 bushels). The contents of that patent are incorporated by reference in their entirety herein. The dryer disclosed in U.S. Pat. No. 5,893,218 allows flexible control of air temperature by providing hot and cold air plenums with controllable gates to mix air to desired temperature. Air flow direction can also be reversed and rate of air flow can be adjusted.
Although this system provides highly flexible control of air temperature, there is still a need for improvement in such a drying process.
Drying of small lots of ear corn is not a matter of how to most quickly dry the ear corn. Rather it is the quality of drying that is important. By this it is meant that, optimally, drying should proceed at a certain rate; or stated differently, quality of the dried seed is related to the rate of moisture removal during drying. This depends on the nature and type of material and its initial moisture content. Presently, manually collected moisture samples are taken during the drying process to check on drying rate. The rate of the air flow is normally adjusted based on those samples. This is time consuming and cumbersome. Therefore, there is room for improvement in the art.
It is thus a primary object of the present invention to provide an apparatus and method for drying of small lots of product which overcomes or improves over the problems and deficiencies in the art. Further objects, features, and advantages of the present invention include a method and apparatus as above-described which:
1. Allows automation of the drying process.
2. Provides a higher degree of flexibility and selectability of variables during drying.
3. Allows precise control of rate and temperature of air flow while allowing automated monitoring of moisture in the product.
4. Allows individual control of drying of multiple small lots.
5. Maximizes the quality of drying of the product and therefore the quality of the product.
6. Allows for automatic acquisition of drying process data for use in quality assurance documentation and decisions.
7. Provides for an improved level of process control for drying.
8. Improves the efficiency of time and resources utilized in drying.
9. Is efficient, economical, and durable.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.